Lovastatin is the first approved hypocholesterolemic drug in a new class which act to inhibit cholesterol biosynthesis and reduce plasma concentrations of low density lipoprotein. No systematic studies have been conducted to date to examine the efficacy and safety of this drug in children. Adolescent boys aged 10-17 with heterozygous familial hypercholesterolemia will be enrolled in this study which will be a placebo controlled trial of diet plus lovastatin versus diet plus placebo. This initial study will last for one year.